Field of the Invention
The invention relates to a sensor device for recording moisture on a window, with a transmitter and a receiver and with an optical unit arranged between the transmitter and the receiver, wherein the optical unit comprises an optical input unit facing the transmitter, an optical output unit facing the receiver and a coupling-in and coupling-out region on the side of the window pane.
Brief Description of the Related Art
Such sensor devices serve to record moisture on window panes, in particular on windscreens of motor vehicles. They are used to ascertain, whether drops or water are present on the window pane, and then to control a windscreen wiper on the basis of this information. Headlight control is also feasible.
A generic sensor device is known from the DE 40 06 174 C1. The windscreen has an optical unit arranged on it, where radiation, in particular light, is emitted from a transmitter into the optical unit at one end. The radiation is reflected a number of times in the optical unit and in the window pane in contact with the surface of the optical unit. Depending on the degree of wetting of the window pane, the rays are coupled out of the pane. The other end of the optics has a receiver arranged on it, which supplies a signal inversely proportional to the amount of precipitation. The sensor device operates according to the optical principle of total reflection. A further similar sensor device is known from the DE 10 2013 009 126 A1.